In this study, interpretation of float-sink test data has been performed by simple equations on pumice of different origins with different porosity. At the outset, the cumulative weight and the percentage porosity of the floating fraction have been determined for the pumice samples at all the different levels of relative densities that were tested. The derivations of equations, the recoveries in cumulative floating part have been calculated. Then, the relationship between the recoveries and relative densities has been stated as simple equations and the values calculated from equations have been compared with the experimental results. Furthermore, it has been found that these types of equations are suitable for the interpolation of sink-float data. In conclusion, the results obtained from float-sink tests can be expressed quantitatively by simple curve fitted equations with respect to porosity variation. © 2005 Institute of Materials, Minerals and Mining and Australasian Institute of Mining and Metallurgy.